The present invention relates to a multipin electronic plug of the type used, for instance, on a computer-printer cable. More particularly this invention concerns a block that carries a single row of pins associated with respective terminals and that is used in the manufacture of such a plug.
A standard multipin electronic plug has a body with several rows of pins that fit into respective conductive holes of a complementary socket. Each pin is associated with a respective terminal to which a wire or printed-terminal contact is soldered. Two rows of terminals are normally used, although a greater number of rows is employed in special situations.
The basic element for making such a multipin electronic plug is a terminal/pin block having a rigid dielectric plate lying in a plane and having a pair of edges and two opposite faces and a row of conductive strips imbedded in the plate. The strips all lie in a common plane parallel to each other and each have one end forming a contact pin and an opposite end forming a terminal. The contact pins all extend from one of the edges of the plate and the terminals all extend from the other of the plate edges. Each pin end is slim and of uniform shape and section, and each terminal end often has a wire- or solder-holding split. The strips may be straight or nonstraight, for instance L-shaped, when the terminals project crosswise to the pins.
Such a terminal/pin block is made by first stamping out of sheet metal the row of conductive strips with flashing left between them to maintain their spacing. This stamped-out part is then cast into a plastic plate from which the terminal and pin ends project, the flashing being provided at the projecting portions. Then the flashing is punched out, leaving the strips fixed in the plate but electrically isolated from each other.
To make the multipin plug, at least two such terminal/pin blocks are encased in a mold and positioned therein such that the pins and terminals are at the desired orientation relative to one another. Then more plastic is injected in to form around the plates a larger plastic body from one edge of which projects several rows of pin ends and from another edge of which project several rows of terminal ends.
The problem with this style of manufacture is that the terminal/pin blocks often shift during the final molding operation so that the pins become misaligned and cannot fit a standard plug. This misalignment is normally caused by the high pressure of the plastic injected in a high-speed operation into the final mold so that, even if the blocks are perfectly positioned as the mold is closed, the incoming resin displaces them during the molding operation.
It is therefore an object of the present invention to provide an improved terminal/pin block for a multipin electronic plug.
Another object is the provision of such an improved terminal/pin block for a multipin electronic plug which overcomes the above-given disadvantages, that is which can be manufactured at high speed without producing misaligned contact pins.
A further object is to provide an improved method of making a multipin electronic plug.
A terminal/pin block for making a multipin electronic plug has a rigid dielectric plate lying in a plane and having a pair of edges and two opposite faces. According to the invention respective centering formations formed on the faces project away from the plane and the centering formations of one of the faces are complementary to and fittable in the centering formations of the other of the faces. A row of conductive strips imbedded in the plate all lie in a common plane parallel to each other and each have one end forming a contact pin and an opposite end forming a terminal. The contact pins all extend from one of the edges of the plate and the terminals all extend from another of the plate edges.
The method of this invention therefore involves the steps of embedding in the above-defined rigid dielectric plate the row of conductive strips with the strips all lying in the plane parallel to each other and with the pins extending from one plate edge and the terminals from the other. Each of the faces of the plate is formed with at least one respective centering formation projecting away from the plane with the centering formations of one of the faces complementary to and fittable in the centering formation of the other of the faces. A plurality of the plates are stacked with the pins extending parallel to each other and the formations of adjacent plates interfitting and impeding movement of the plates relative to each other parallel to the plane. Then the stacked plates are enclosed in a mold cavity with the pins and terminals outside the mold cavity, and the mold cavity is filled around the plates with a molten dielectric plastic that is hardened into a plug body.
The centering formations according to the invention prevent any shifting of the blocks during the molding operation. Thus in the finished product the pins and terminals will be perfectly positioned.
According to the invention the plate is generally square and has four corners and the formations are at the corners. Furthermore the formations of the other face are formed as seats into which the centering formations of the one face can fit for stacking of the blocks. These formations have planar outer end faces extending parallel to the plane.